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Chai Discovery Raises $400 Million Series C at $3.8 Billion Valuation as Pfizer, Lilly and Novartis Deals Pile Up

AI drug-design startup Chai Discovery raised $400 million at a $3.8 billion valuation, nearly tripling its worth in seven months as Pfizer, Eli Lilly and Novartis sign on.

Biotech & Medicine Drug Development
startups funding AI drug discovery biotech venture capital
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Editor's Note ·

Correction:
The article attributes the quote "the first zero-shot generative platform for fully de novo antibody design to achieve double-digit experimental success rates" — describing the Chai-2 model — to SiliconANGLE. That exact sentence does not appear in the SiliconANGLE article; it is from BioSpace's Series C press release ('Chai Discovery Announces $400M Series C to Advance AI-Driven Molecular Design'), which the article separately cites. Part of the extended investor list in the same paragraph (Glade Brook, Avenir, Lachy Groom and Yosemite) is likewise only found in that BioSpace release, not in SiliconANGLE's reporting.
Correction:
The article states the Novartis collaboration 'extends work that began over a year prior, including early access to Chai's next-generation folding model in spring 2025,' presented as a direct quote from BioSpace. The BioSpace release actually reads: 'The agreement builds on more than a year of technical engagement between the two companies, including early access to Chai's next-generation folding model last spring' — a paraphrase, not a verbatim quote, and it does not specify a year. Given the release's July 13, 2026 publish date, 'last spring' more plausibly refers to spring 2026, not spring 2025 as stated in the article.

Overview

Chai Discovery, a San Francisco startup that builds AI models for molecular design, has raised $400 million in a Series C round that values the company at $3.8 billion, according to SiliconANGLE. The round was led by Index Ventures, with Kleiner Perkins, Sequoia Capital and Dimension co-leading, according to BioSpace. The financing lands shortly after Chai announced a new collaboration with Novartis, adding to existing commercial agreements with Pfizer and Eli Lilly.

What We Know

New investors in the round include Bain Capital Ventures, Battery Ventures, Baillie Gifford, BDT & MSD, Sapphire Ventures and Avra Capital, joining existing backers Thrive Capital, OpenAI, Oak HC/FT, Menlo Ventures, General Catalyst, Glade Brook, Avenir, Lachy Groom and Yosemite, according to SiliconANGLE. The new valuation is nearly triple the $1.3 billion mark Chai reached in a $130 million round in December 2025, and the Series C brings the company’s total funding to about $630 million to date, SiliconANGLE reported.

Chai Discovery was founded in 2024 in San Francisco by Joshua Meier, Jack Dent, Matthew McPartlon and Jacques Boitreaud, whose backgrounds span OpenAI, Meta FAIR, Stripe and academic research, according to BioSpace.

“Tomorrow’s medicines should be designed with the precision, speed and scale of modern engineering, and this support helps us move faster towards that future,” said co-founder and Chief Executive Joshua Meier, according to SiliconANGLE.

The company’s Chai-2 model, released in 2025, was “the first zero-shot generative platform for fully de novo antibody design to achieve double-digit experimental success rates,” according to SiliconANGLE. Its successor, Chai-3, “materially improves target success rates and binding affinity compared to its predecessor,” the outlet reported, producing antibodies that “bind substantially more tightly to intended targets,” according to BioSpace.

Big pharma has followed the technology. Chai signed “a landmark licensing agreement with Pfizer Inc., granting access to Chai-3,” and a customer agreement with Eli Lilly, according to SiliconANGLE. Shortly before the Series C was announced, Chai unveiled a “formal collaboration” with Novartis, according to SiliconANGLE, under which the pharmaceutical company “gains access to Chai Discovery’s AI models to support therapeutic antibody discovery across multiple targets,” according to BioSpace. The agreement “extends work that began over a year prior, including early access to Chai’s next-generation folding model in spring 2025,” the outlet reported. Financial terms of the Novartis agreement were not disclosed, according to BioSpace.

“This is a significant step forward in expanding the range of therapeutic programs that can benefit from AI-driven molecular design,” Meier said of the Novartis deal, according to BioSpace. Fiona Marshall, President of Biomedical Research at Novartis, said applying Chai’s models to challenges like antibody design lets the company “explore a broader range of possibilities, make better decisions earlier,” according to the same BioSpace release.

Chai’s raise comes amid a broader capital rush into generative AI drug discovery. Despite roughly $20 billion invested in the field, no AI-discovered drug has yet won regulatory approval, and there are now more than 173 AI-originated drug programs in clinical development, up from almost two dozen in 2023, according to SiliconANGLE, which cited figures from AI life-sciences firm Excelra Knowledge Solutions and the news site OncoDaily.

What We Don’t Know

Neither Chai nor its pharma partners have disclosed the financial terms of the Pfizer, Eli Lilly or Novartis agreements. It is also not clear from the announcements whether any Chai-designed antibody candidates have yet entered human clinical trials, or on what timeline any might reach regulatory review.